Jan. 19, 1960
2,922,023
R. L. HACKMAN ETA!
ELECTRIC ARC PROCESS AND APPARATUS
Filed Dec. 17, 1956
D.C
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POWER
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GAS
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TACTOR
INVENTORS
ROBERT L. HACKMAN
RAYMOND P. SULLIVAN
By QMKL/w
A T TORNEV
United States Patent 0
ICC
2,922,023’
Patented Jan. 19, 1960
2
the torch is positioned. Again there are two distinct
choices: (1) ?nely-divided metal or (2) metal with a
?nite form. The ?rst choice has been rejected by us
for practical purposes. Finely-divided metal will tend to
be disbursed by the shielding gas unless the metal is held
in place with a binder. The second choice can, of course,
2,922,023
ELECTRIC ARC PROCESS AND APPARATUS
Robert L. Hackman, Morris Plains, and Raymond P. S_ul
livan, Jersey City, N.J., assignors to Union Carbide
Corporation, a corporation of New York
Application December 17, 1956, Serial No. 628,660
16 Claims. (Cl. 219-74)
take many forms such as:
(1) Small discs of metal which can be completely
fused into the weld.
10
(2) A waster sheet placed on top of the weldment from
which sheet metal is fused downward into the weldment
and the excess sheet is later removed.
(3) Bars of metal having very small cross section.
(4) Thin strips of metal, which is a combination of
This invention relates to electric arcs and more par 15 Methods 2 and 3.
ticularly to the use of a pilot high-pressure arc for
All four of the above methods have been tried and
starting and aiding a gas shielded arc working operation.
found to work by us; however, some are more practical
In its simplest form, according to the invention, there
is provided a novel process which comprises igniting a
pilot high-pressure are between spaced electrodes, apply
ing such pilot arc to a workpiece that is electrically neu
tral with respect to such arc, and electrically transferring
‘such pilot arc to the workpiece by applying substantially
the same relative potential of one of said electrodes to
such workpiece.
More particularly the invention comprises feeding inert
gas to an are spot welding torch including a central elec
trode surrounded in spaced concentric relation by an
electrically “hot” nozzle from which such gas is dis
charged, and striking a pilot high-pressure arc between
than others. Method 1 requires exact positioning; Meth
0d 2 involves considerable metal waste in the unused areas
of the waster sheet and some di?iculty may be encountered
in peeling off the sheet; and Methods 3 and 4 involve less
metal loss and positioning is easily accomplished by
positioning slots in the bottom of the gas cup or an in
sulated positioner template. The unfused metal remain
ing on the weldment from Methods 3 and 4 is easily
removed.
Method 4 of metal addition described above has solved
the problem best for this particular welding application.
However, all four methods of metal addition can be
utilized with our novel pilot arc method of starting for
both are spot- and seam-welding.
such electrode and said nozzle, the ef?uent of which arc
is discharged with such gas from such nozzle. Such
Pilot high-pressure are starting, in which the gas nozzle
discharged pilot arc e?'luent is applied to electrically con
or cup is an electrode of the pilot arc, is superior to high
ductive work that is electrically neutral with respect to
frequency pilot arc starting for several reasons. With
such pilot arc e?iuent, and the nozzle is moved into 35 pilot high-pressure are starting there is no high-fre
direct contact with such work, causing such pilot arc
quency radiation, there is a greater degree of starting
to transfer electrically from the nozzle to the work as an
reliability, and torch design complications are reduced
electrode. Such work is melted in the area within such
because it is not necessary to design against internal
nozzle by increasing the current of such arc in circuit with
high frequency leakage or arc-over. Opposed to the dis
40
said work to produce a spot weld therein when the op
advantages of high-frequency pilot are starting, pilot
eration is ?nished.
high-pressure are starting, particularly according to the
Where pilot are starting has been used in the past it
present invention, includes the desirable possibility of
has been generally understood that the gas cup or nozzle,
preheating and postheating. In addition we have dis
when it is an electrode for such pilot arc, should be elec 45 covered that the ‘postheating cycle by the pilot high-pres~
trically insulated from the work at least by an air gap.
sure are et?uent as a rule, completely melts the waster
We have discovered, however, that this is not necessary.
strip free of each weld button. This cannot be accom
Thus, a so-called electrically “hot” pilot arc cup need
plished when using high frequency pilot arc for starting.
not be insulated from the work and, in fact, can be de
In the drawings:
liberately brought into actual physical or electrical con 50
Fig. 1 is a fragmentary perspective view, with parts
tact with the work without extinction of the pilot are or
broken away and shown in section, of an inert gas~shielded
any other detrimental effect. Also, in welding, according
‘to the invention, such pilot arc serves the unexpectedly
refractory electrode arc spot-Welding set-up illustrating the
invention;
useful purposes of preheating and postheating.
Figs. 2 and 3 are fragmentary top and bottom plan
The invention solves a problem involving the spot 55 views of work spot-welded with the set-up of Fig. 1;
welding together of three ‘sheets of thin stainless steel,
Fig. 4 is a circuit diagram of the invention; and Fig. 5
for example, in which the maximum indentation or crater
is a fragmentary view in section of a preferred form of
ing permissible is 0.003 in. since the top sheet is the air
our electrically “hot” cup.
foil surface of a supersonic aircraft. Naturally, high
An inert gas-shielded arc torch Iii, such as that shown
and consistent shear strengths are demanded of such spot_ 60
by Kane and Pilia in their patent application Serial No.
welds. It has been found that unless a backup is used
which would greatly complicate manufacture, it is neces
sary to allow the weld underbead to project approxi
mately 0.010 in. below the bottom sheet. Such degree
of penetration has been found requisite to high shear 65
560,117, ?led January 19, 1956, now Patent No. 2,863,
983, which is owned by the assignee of the present case,
is provided with a stick-type thoriated-tungsten electrode
12 that is connected by a conductor 14 to the negative
(—) side of a direct current power source 16. The
positive (+) side of such source is connected to the work
in the undesirable effect of more than 0.003 in. crater or
sink in the top of the weld. Faced with these results,
18 through a conductor 20 provided with a switch 22;
our solution also involves the addition of ?ller metal
and to a gas nozzle or cup 24 composed of metal through
to make up the loss from weld sink.
70 a conductor 26 containing a resistor 28. Inert shielding
Alternate methods of metal addition involve placing
gas 30 such as argon is delivered to the cup 24 and flows
the metal in position over the point to be welded ‘before
‘outwardly therefrom in an annular stream about the arc
strength. However, such degree of penetration results
"2,922,023
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3
the work 18.
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the high potential presented by high-frequency current.
end of the electrode 12 and over the adjacent areas of
(3) There is no, practical limitatlon in a torch cable
_
In spot-welding applications wherein the cup is
length when using pilot high-pressure arc starting. When
touched to the work for the purpose of exerting pressure
on the workpieces to be spot-welded,'we, have found it
desirable, as shown in Fig; 5,’ to provide counterbores
or countersinks, 3133, on the inner diameter of the
high-frequency starting is used, the limits of the torch
cable are determined by the capacitive attenuation of
the high frequency per unit length of cable. In other
words, if the cable has sufficient length, no high frequency
will arrive at the torch end.
end face of the cup 24. Repeated arcing between the
(4) Although not applying to spot-welding but only to
electrode 12 and 'the cup 24 may result in some erosion
of the inner surface of the cup at the end face. The 10 straight inert gas-shielded arc applications, metal cups
counterbores cause the pilot arc to are from the elec~
can be used in all applications. When using high fre
trode to a point in the cup removed from the end face.
Thus, a ?at surface 35 is maintained on the annular
welding applications.
quency, ceramic cups are required in certain manual
_
The form of pilot are starting which is preferred by
end face of the cup for the presentation of a pressing
force on the workpiece equally distributed about the end 15 us is, therefore, a' pilot high-pressure are between elec
face of the cup.
trode and cup.
7
1 .The wall of the cup is also provided with lateral gas
‘outlet ports or vents 37, for the escape of gas when the '
noted in Fig. 2, showing a portion of the waster strip
32 removed and the weld buttons 49 ground ?ush, that
some slight undercutting or sink is still visible. The
picture is somewhat deceiving in this respect for examina
tion of the actual weld sample shows that the irregulari
ties in the surface of the metal about the weld nuggets
end of the. cup is brought into .actual physical and elec
trical contact with the work in the manner set forth
below.
>
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Figs. 2 and 3 show a series of spot-Welds which have
been prepared according to the invention. It- will be
.
A step-by-step description of the operation, Fig. 1,
is as follows: A waster strip 32 is positioned over the
.centerline of the intended spot-welds. An insulator-po
are so slight that they can be barely detected when rub
bing the ?nger over the ground surface of the Weldment.
It should also be noted that this picture was prepared
before the discovery that the post pilot are heat was
sufficient, in most cases, to completely melt the waster
sitioning template 34 is then centered over the waster
strip 32 and secured in place. With a pilot high-pressure
arc arcing between the electrode 12 and the cup 24 the
.torch 10 is brought down so that the cup ?ts in a hole
36 in the template 34 so that notches 38 in therim of
the cup receive the waster strip 32. The notches 38 30 strip free from the weld button. In most cases, even
without pilot post heat, there is very little metal joining
are located in the cup 24 so that the remaining rim
the waster strip to the weld button.
of the cup will rest squarely and uniformly on the sur—
The automatic spot welding control, as shown in Fig. 4
face of the work 18.
a
consists basically of a starting circuit 42, ?ve timing cir
As the torch 10 approaches the work 18, which is
cuits 43-47, a gas control circuit 49, and press mecha
electrically neutral, the pilot arc will continue to are
nism 48. The starting circuit 42 is arranged so that in
‘between the electrode 12 and the cup 24 until the cup
setting up the operation, the starting circuit 42 energizes
touches the work, at which time, since the electrode-t0
a primary contactor of a D.C.power source or welder cir
waster strip distance is less than the electrode-to-cup dis
tance and since the cup by virtue of coming in contact 40 cuit 16, power being supplied by mains 50 connected di
rectly to the welder circuit 16. Simultaneously the start
with- the work places it at the same electrical potential
ing circuit 42 energizes the gas control circuit 49 so that
as the cup, the pilot arc jumps directly to the work as an
at least 3 c.f.h. of shielding gas is provided for the pilot
electrode. 'When the switch 22 is closed to increase the
‘arc in the torch. The pilot arc is then struck between the
welding current, the welding arc follows the same path
ends of electrode 12 and cup 24. The Welding control
as the pilot arc, melting the work under the arc, and
45 and associated apparatus are thus readied for the welding
the waster strip is melted into the weld puddle.
operation. The operation of the starting circuit 42 is
When the weld cycle is completed and a timing device
initiated by operating a suitable switch and, in turn, causes
opens switch 22, the weld is completed, but the pilot arc
the pre-?ow timer 43 to start timing an increased flow of
,continues to are between a completed spot-weld button
gas. The pre-?ow timer 43 controls the amount of time
40 and the torch electrode 12. At such time the heat
supplied by the pilot are generally results in the com 50' the volume of gas required for welding is ?owing prior
plete separation of the waster strip 32 from the weld
to the start of the welding action.
button. As the torch 10 is lifted from the work 18 the
_The squeeze timer 44, which controls the press mecha
‘pilot arc jumps back to the cup 24, as an electrode, since
nism 48, may start its squeeze simultaneously with the
the work 18 no longer has any electrical connection in
55 pre-?ow timer 43, or may proceed, or follow it, in time
the welding circuit. Thus, it can be seen, that placing
sequence. When the squeeze timer 44, through its action
the metallic gas cup 24 directly against the work 18 acts
on the press mechanism 48, has caused the gas cup 24 to
be pressed against the work for a predetermined time,
the squeeze timer 44 energizes the weld timer 45. In turn,
ing point for the pilot arc. The D.C. power source 16 is
60 the weld timer 45 closes the welding contactor switch 22,
'a conventional D.C. welding power source, while the
so that the welding circuit is completed and the welding
as a switch to bring the work to the same electrical po- .
.tential as the cup and thus produces an alternative arc
resistor 28 serves to limit the pilot arc current.
arc is drawn on the workpiece 18.
Pilot high~pressure are starting according to the in
At the completion of the welding cycle, the welding
timer>45 de-energizes the welding contactor switch 22,
high-frequency starting for both inert gas-shielded are
65 causing it to open, and simultaneously energizes the hold
spot and seam welding. They are as follows:
timer 46. This timer, 46, controls the length of time that
(1) By virtue. of the presence of the pilot high-pressure
the gas cup is pressed against the work after the main
arc the electrode is maintained at a constant temperature
welding action has been completed. When the hold timer
vention oifers a number of additional advantages over
and a constant dimension, resulting in more uniform
spot welds and, in the case of mechanized applications
where voltage control is not used, there is far less danger
of electrode growth, resulting from heating, causing a
‘shortening of the arc length as the weld progresses.
,_
(2) There is no electrical shock hazard connected
46 is timed out, it actuates the press mechanism 48 so that
70 the gas cup is withdrawn from the work.
The post-flow timer 47 may be actuated simultaneously
with the hold timer, or at some later point in time. Upon
completion of the post-?ow timing cycle, the post-?ow
timer 47 actuates the gas control circuit 49 so that the
with'use of pilot high-pressure, are starting as opposed to 75 gas ?ow is reduced from the amount required for weld
9,922,029
.
5
ing to the amount required for maintenance of the pilot
are only.
In some cases the welding cycles may follow after each
other ‘in such rapid succession that there is little economic
The term "high-pressure” are as used herein is discussed
(pages 290 and 326) by Cobine in his book, “Gaseous
Conductors,” published in 1941 by McGraw-Hill and is
to be understood to relate to self-sustaining gas dis
vadvantage in attempting to reduce the gas ?ow during the
charges in the general pressure range of 1,50 to several
non-welding portion of the overall cycle. In these cases
atmospheres and generally in the current range of a few
the pre-?ow and post-?ow timers may be eliminated.
to many of amperes.
The following is ‘a brief recapitulation of the operation
What is claimed'is:
of the automatic spot welding control shown in Fig. 4:
1. Process which comprises igniting a pilot high-pres
The starting circuit 42 energizes the primary contactor 10 sure are between spaced electrodes, applying such pilot
"switch 22 and actuates the gas control 49 so that at least
'3 c.f.h. of argon is ?owing through the torch. The pilot
are is then struck. The sequence is then started with a
arc to a workpiece that is electrically neutral with re
spect to such are, and electrically transferring such pilot
arc to the workpiece by applying substantially the same
pre-?ow of gas controlled by the pre-?ow timer 43. This
relative potential of one of said electrodes to such work
timer actuates the gas control 49 so as to increase the
piece.
shielding gas ?ow to a rate suitable for the main welding
action. Simultaneously, ‘the squeeze timer 44 is actuated
and, in turn, operates the press mechanism 48 to press the
2. Process which comprises igniting a pilot high-pres
sure are between spaced electrodes, applying such pilot
arc to a workpiece that is electrically neutral with respect
torch gas‘cup 24 against the workpiece 18.
to such arc, and electrically transferring such pilot arc
At the end of the squeeze time, the weld timer 45 is 20 to the workpiece by applying substantially the same rela
started and, in‘ turn, actuates the weld contactor 22 switch
tive potential of one of said electrodes to such workpiece
closing the main welding circuit. Upon completion of
and electrically energizing a transferred power high-pres
the welding cycle, contactor switch 22 opens and the
sure arc between such workpiece and the other electrode.
hold timer 46 maintainsapost-welding pressure against
3. Process as de?ned by claim 2, in which such power
the workpiecelS and then actuates the press mechanism 25 are is discontinued While the transferred pilot arc is con
48 to release the gas cup pressure on the work 18. The
tiuued until the workpiece is again made electrically neu
post-?ow timer 47 is actuated; and upon completion of
tral causing the pilot arc to return to such spaced elece
the time cycle, actuates the gas control 49 so as to reduce
thegas ?ow to the vidling gas ?ow required for the pilot arc.
As an example'jo'f an actual automatic welding opera
tion according to the invention in which a waster strip is
not used, the following conditions are representative:
centric relation by an electrically conductive nozzle
from which such gas is discharged, striking a high-pres
sure arc between such electrode and said nozzle, the
Table I
35 e?luent of which are is discharged with such gas from
Main arc current ...._- 160 A. DC-SP.
Time ________ _. 110 cycles (1 cycle=1/60 sec.).
Length _______ _. 0.072 in.
Voltage ______ __ 70-80 volts (open circuit).
Pilot arc current ____.
Time ________ .._
Gas-kind _______ __
Pilot arc ?ow -__
trodes and become electrically non-transferred with re
spect to the workpiece.
4. Process which comprises feeding gas to an arc torch
including a central electrode surrounded in spaced con
10 A. DC-SP.
Operating constantly.
Argon (commercial grade).
3 cu./ft./hr.
such nozzle, applying such discharged arc e?luent to an
electrically conductive member that is electrically neu
tral with respect to such are effluent, and switching said
nozzle and such member into the same polarity with
40 respect to each other, causing such are to transfer from
the nozzle to the member as an electrode.
5. Process which comprises feeding gas to an arc
torch including a central electrode surrounded in spaced
‘concentric relation by an electrically conductive nozzle
10 45 from which such gas is discharged, striking a high-pres
Welding ‘?ow ___ 5-6 cu./ft./hr. (Pre-flow time 10
cycles.
Post-?ow time
cycles.
Electrode ________ __ 1A1 in. D.1-thoriated tungsten. Tip
pointed.
Nozzle #6 _______ _.. % in. l.D.-copper.
sure are between such electrode and said nozzle, the
ef?uent of which are is discharged with such gas from
such nozzle, applying such discharged arc effluent to an
electrically conductive member that is electrically neu
Work-‘Metal _____ _. 2 carbon steel sheets, l-0.044 in. 50 tral with respect to such are e?luent,‘and moving said
thick, l-0.063 in. thick.
1Diameter.
An actual manual spot welding example of the inven
tion is typi?ed by the conditions set forth in the following:
Table II
Waster strip ______ __ 0.025 in. thick, 146 to 3/32 in. wide,
17-7 PH stainless.
Electrode ________ __ 1A; in. D.1-tungsten (thoriated).
Tip pointed.
Main arc current ____ 150 A. DC-SP.
Gap _________ _. 0.060 in.
Time ________ ..-
1.0 sec.
Gas cup:
Contact time __.. 2 sec. ( approx.)
Nozzle #6 _____ % in. I.D.-copper.
Gas: Flow _______ __ Argon, 10 c.f.h. (constant).
Pilot arc _________ _. 10 A. DC-SP. Continuous opera
tion.
Work-metal _____ __ 3 sheets stainless. Top 0.042 in.
thick. Middle 0.035 in. thick.
Bottom 0.025 in. thick.
1Diameter.
nozzle into direct contact with such member, causing
such are to transfer electrically from the nozzle to the
member.
6. Process which comprises feeding gas to an are spot
welding torch including a central electrode surrounded
in spaced concentric relation by an electrically con
ductive nozzle from which such gas is discharged, strik
ing a pilot high-pressure are between such electrode and
said nozzle, the efliuent of which are is discharged with
such gas from such nozzle, applying such discharged
pilot arc e?luent to an electrically conductive member
that is electrically neutral with respect to such pilot arc
e?luent, and moving said nozzle into direct contact with
such member, causing such pilot arc to transfer elec~
65 trically from the nozzle to the member as an electrode,
melting such member in the area Within such nozzle to
produce a spot weld when the operation is ?nished.
7. Process as de?ned by claim 6, in which a strip of
waster metal is disposed between said nozzle and said
electrically conductive member for the purpose of sup
plying additional metal to the spot weld, and making a
well-de?ned circular line of demarcation between such
spot weld and the remainder of such strip by continuing
the transferred pilot are for a predetermined time inter
75 val after the main arc has been discontinued.
17
8
‘
in the rim thereof for ?tting’ a waster strip disposed on
a work electrode for cooperation therewith, and vsaid/noz
8. Process of spot-welding overlapping sheets of metal
with a refractory electrode inert gaseshielded, arc torch
which comprises laying a strip of waster metal onrthe
top of such sheets to‘ be spot-welded, connecting the elec
zle is_ also provided with at leastone lateral vent for
discharging gas delivered'to said nozzle when the-rim of'
trode and cup of such torch to a direct current source,
the latter is pressed into contact with such workelectr'ode.
striking a direct current pilot are between such cup and
13. Process as de?ned by ,claim ,2, in whichthe so
transferred pilot arc is applied to the. workpiece for a
‘predetermined interval of time for the purpose of pre
electrode while discharging inert gas £10m the cup, ap
plying the rim of said cup to said strip with the result
heating the workpiece before said power arc is so trans
that the pilot arc current is transferred to such strip, con
necting said sheets and electrode to a source of welding 10
14. Process as de?ned by claim '3, in which the so
current and thereby striking a main arc between the
ferred»,
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continued transferred pilot arc is so applied tothe'work
piece .forra predetermined time interval for the purpose
of post-heating the workpiece before the pilot arc-‘is so
end of such electrode and 'suchsheets, fusing the metal
thereof adjacent such are, whereupon the operation is
stopped, leaving the sheets spot-welded together.
9. Electric arc spot welding process which comprises
returned to the spaced electrodes. .
0
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'15. Process as de?ned by claim 14, inwhich the ?rst
so transferred pilota'rc is appliedto the workpiece for
a predetermined interval of time for. the purpose of pre
heating the workpiece before said power arc is so trans
applying a metal member on a workpiece in the area to
be welded, and drawing a welding are between an elec—
trode and such workpiece, melting such member in such
area to thereby add metal to the spot weld puddle, while
supplying an annular stream’ of inert gas such as argon
ferred.
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I 16. Gas shielded non-consumable. electrode electric
thereto, with the resultVthat-no sink is left in the weld
when the operation is ‘finished in which the metal member
is__ a strip that is pressed by the rim of a nozzle for such
-gas into direct contact with the workpiece, and the cur-'
arc spotwelding process which comprises striking in an
atmosphere of selected gas an electric-spotvwelding are
.rent of such are is reduced to a predetermined value for
2.5 overlapping a base metal member in circuit relation with
a predeterminedtime interval for the purpose of melting
.the metal of the strip entirely from the latter only in’ the
between a non-consumable electrode and a sheet of metal
.area of the weld so that the remainder of such strip can
such non-consumable electrode, melting a vpuddle of
vmetal in such gas atmosphere with such are in the ad
jacent portion of such sheet, adding ?ller‘ metal to such
puddleby melting a certain predetermined portion of a
10. Process as de?ned by claim 9 in which such re 30 ?ller metal member in such arc adjacent such puddle,
and discontinuing such arc, producting a spot weld be
.duced'currentis conducted to the strip and workpiece
tween such sheet and said baseme'tal member provided
through said nozzle.
. p
only with ?ller metal that is so fused to'?ll the weld in
11. Electric arc welding apparatus comprising, in com
dentation that otherwise would be left in such spot weld
bination, an electrode consisting of gas nozzle having an
inner annular surface,’ and another electrode depending 35 with such predetermined certain portion of said ?ller
metal member.
centrally within said nozzle, providing an annular gas pas
sage therebetween, means supporting said nozzle and
electrode electrically insulated from each other, charac
References Cited in the ?le of this patent
terized in that such inner surface of the nozzle is pro
be removed from the workpiece after the operation.
vided with at least one annular step the diameter of 40
which is less than that of the end surface of the nozzle,
for carrying an arc between the nozzle and said central
electrode.
12. Electric arc welding apparatus comprising, in com
bination, an electrode consisting of gas nozzle having an 45
inner annular surface, and another electrode depending
centrally within said nozzle, providingrran annular gas
passage therebetween, means supporting said nozzle and
electrode electrically insulated from each other, charac
‘terized in that said nozzle is provided with alined slots
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Thomson ____________ __ Feb. 3, 1914
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Kjekstad ____________ __
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Herman ____________ __
Pickhaver ___________ __
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Douglas _____________ __ Mar. 8,1955
'AndersonIu; ________ __' Oct. 25,1955